Chamfer bits make a single kind of cut — a straight angled edge — but, depending on the bit’s cutter angle, you can make it do a number of tasks. A 45-degree chamfer bit can create perfect miters for boxes. Other angles can be used for coopering (a 11.25-degree bit makes the correct edge angle for a 16-segment polygon). Like a roundover, a chamfered edge can ease sharp corners. Laminate installers often use a chamfer on countertop edges.
Available cutter angles depend on the manufacturer, but you should be able to easily find 11.25, 15, 22.5, 25, 30 and 45 degrees. You’ll probably use a 45-degree chamfer more than any other. Since the size of a chamfer is controlled by how far the bit is extended from the router, it’s not surprising that there are somewhat fewer sizes of chamfer bits available than other styles.